1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a cylindrical member in the form of a cylindrical substrate having a coating layer formed thereon.
2. Related Background Art
In some processes for manufacturing a cylindrical member in the form of a cylindrical substrate having a coating layer, e.g. a process for manufacturing an organic photosensitive member for electrophotography in the form of a cylindrical substrate having a coating layer such as a photosensitive layer formed thereon, the coating layer is formed in the following manner. That is, a coating liquid such as a liquid solution for forming the photosensitive layer is applied on the substrate, and then the coating liquid is dried (i.e. the solvent in the coating liquid is evaporated) utilizing induction heating at a high frequency so that the coating layer is formed. Conventionally, such induction heating has been performed by supplying a high frequency current to an excitation coil that is wound in such a way as to surround the photosensitive member for electrophotography externally as shown in FIG. 18 (see e.g. Japanese Patent Application Laid-Open No. 9-114111).
In the arrangement shown in FIG. 18, a cylindrical substrate 3 made of an electrically conductive material is loosely inserted into an excitation coil 1xe2x80x2 in such a way as to be coaxial with the coil 1xe2x80x2. On the outer peripheral surface of the cylindrical substrate, coating liquid 4 for forming a coating layer has been applied. The cylindrical substrate 3 is held by a chuck 25 of a lifting apparatus 24 so as to be moved up and down. While the cylindrical substrate 3 is moved up and down by the lifting apparatus 24 and rotated by a rotating mechanism (not shown), it is subjected to induction heating by the excitation coil to which a high frequency current is supplied from a high frequency oscillator 26 via a matching device 22. The temperature of the cylindrical substrate 3 is monitored by an optical fiber type radiation thermometer 23. The detection signal of the optical fiber type radiation thermometer 23 is fed back to the high frequency oscillator 26 via a control apparatus 21, so that the temperature of the cylindrical substrate 3 is controlled to be a predetermined value.
In the arrangement in which the excitation coil is provided outside the photosensitive member for electrophotography (as in the case of the above-described arrangement), a high degree of accuracy in the distance between the excitation coil and the coating liquid is required, since there is a risk that the excitation coil could touch the surface of the coating liquid and damage it.
Furthermore, in the induction heating, the cylindrical substrate is caused to generate heat in order for the coating liquid to be dried at the interface between the substrate and the coating liquid, and so the solvent in the coating liquid evaporates to the exterior of the substrate. So in the arrangement in which the excitation coil is disposed outside the cylindrical substrate, the presence of the coil is apt to disturb the drying or evaporation to invite non-uniformity in drying. This might adversely affect images to be formed on the photosensitive member.
In addition, with the evaporation of the solvent, its concentration in the circumferential atmosphere will increase. This invites a risk of catching fire when the temperature of the excitation coil is increased by its own operation.
On the other hand, in the arrangement in which heat required for a cylindrical member is generated locally, a complex mechanism and a complicated controlling process are necessary for moving the excitation coil up and down relative to the cylindrical member.
Drying methods that utilize heated air have been also conventionally adopted as simple methods for drying coating liquid (see e.g. Japanese Patent Application Laid-Open No. 10-239868). However, such methods are suffering from various disadvantages such as slowness in raising the temperature of a cylindrical substrate up to a prescribed temperature, non-uniformity in the temperature on the cylindrical substrate and a risk of catching fire due to the heated air when a solvent is used. Therefore, such methods are not suitable for manufacturing the cylindrical member, especially when reduction of the manufacturing time is desired.
An object of the present invention is to provide a method and an apparatus for manufacturing a cylindrical members that can produce cylindrical members safely with small variation in their qualities and at an advantageous cost.
A method according to the present invention is a method for manufacturing a cylindrical member including a cylindrical substrate and at least one coating layer thereon, comprising:
an applying step of applying a coating liquid on the cylindrical substrate; and
a drying step of drying the coating liquid that has been applied in the applying step by an induction heating means to form the coating layer;
wherein,
the induction heating means is disposed in the interior of the cylindrical substrate;
the induction heating means includes an excitation coil to generate a magnetic flux in a direction perpendicular to the axial direction of the cylindrical member; and
the excitation coil is disposed along the inner surface of the cylindrical substrate.
An apparatus according to the present invention is an apparatus for manufacturing a cylindrical member including a cylindrical substrate and at least one coating layer thereon, comprising:
an applying means for applying a coating liquid on the cylindrical substrate; and
a drying means for drying the coating liquid that has been applied by the applying means by induction heating to form the coating layer;
wherein,
the drying means includes induction heating means for performing induction heating;
the induction heating means is disposed in the interior of said cylindrical substrate;
the induction heating means includes an excitation coil to generate a magnetic flux in a direction perpendicular to the axial direction of the cylindrical substrate; and
the excitation coil is disposed along the inner surface of the cylindrical substrate.